Many Sterile Worker Bees Give Their Lives to Save a Beehive

Many sterile worker bees give their lives to save a beehive from an attack by bears,etc.In such cases,we now know

A) these female worker bees are more related to hive offspring than they would be if they were fertile and mated; it is "calculated selfishness."
B) this is really a case of bees consciously understanding the need to preserve the nest for their individual benefit and they might survive if all work together.
C) each female worker is waiting to get her chance to reproduce.
D) this is a case of sexual selection.
E) the system is not yet understood.